The aforementioned copending application, Ser. No. 08/082,199 and its parent applications relate to a tamper-evident tape for application over the flap or other opening in pouches, bags, envelopes and the like, which tape will provide evidence of tampering over a wide temperature range from above to below the Tg of the adhesive layer adhering the tape to the substrate to be protected from tampering.
As is described and claimed therein, the tamper-evident adhesive tape comprises a transparent backing layer carrying on one side thereof, in order:
(1) a discontinuous layer of deposits of a transparent barrier material bonded to the backing; PA1 (2) a colored layer chemically bonded to the backing layer in areas where there are no barrier material deposits, the barrier material preventing chemical bonding of the colored layer to the backing layer in areas where the barrier material is present; and PA1 (3) an acrylic pressure sensitive adhesive layer for securing the tape to the container where any evidence of tampering is desired, the chemical bond strength between the backing layer and colored layer being greater than the adhesion strength between the colored layer and the adhesive layer securing the tape to the container both above and below the Tg of the adhesive layer, whereby when attempt is made to remove the tape from the container to gain access to its contents, the colored layer will remain with the backing in areas where they are chemically bonded while in areas where barrier material is present to prevent chemical bonding, the colored layer will adhere to the adhesive layer to provide a colored pattern or image evidencing tampering with the container which is visible to the eye, which evidence remains visible to the eye when an attempt is made to reapply the colored layer and backing to the adhesive layer. PA1 (1) a discontinuous layer of deposits of a transparent barrier material; PA1 (2) a colored layer chemically bonded to the backing layer in areas where there are no barrier material deposits. PA1 (3) a pressure-sensitive adhesive layer tailored to possess a cohesive strength weaker than that of the substrate to which the tape is to be applied; and PA1 (4) an acrylic pressure-sensitive adhesive layer for securing the tape to the substrate.
A tamper-evident tape embodying the aforementioned invention and which is manufactured and sold by The Kendall Company, assignee of the instant invention and of the aforementioned earlier applications, has achieved considerable commercial success. However, it has been found that while the tape is entirely efficacious for use on plastic substrates, it should not be employed on substrates whose cohesive strength is smaller than the adhesion between any of the layers of the tape, e.g. substrates such as paper products, corrugated containers, cardboard containers, shipping canons and other such cellulosic materials.
Accordingly, stated simply, the task of the present invention can be said to modify the aforementioned commercially available tamper-evident tape currently employed with pouches, bags, envelopes or other plastic containers for currency, security documents and the like, to provide a tape which can be employed as a tamper-evident seal for cellulosic materials such as those mentioned above.